Energy expenditure and obesity across the economic spectrum, McGrosky et al. 2025

[Jesse]

I know plenty of people who would count as obese who eat even less calories than I do, going above and beyond to eat well, and have maintained this for months or years, being shamed relentlessly about how lack of discipline must be the cause of their weight.

I've heard these kind of stories before and I don't mean to fully discount them. But I do struggle with understanding them.

I'm also sure it's more nuanced than calories-in calories-out, but I feel like widespread obesity is a pretty recent problem. And GLP-1 drugs appear to work pretty effectively through appetite reduction (unless there's another important mechanism?). Both points do support calories-in and calories-out being the main factors.

That might be part of it, though like I said, I have plenty of examples of people whose jobs keep them on their feet much more than me and certainly have less snacks and smaller meals than me, and yet will still be 100-200 lbs heavier than me.

BMR (Basal Metabolic Rate) can also differ between people, even more so if they're of different size. Then there's also NEAT (Non-Exercise Activity Thermogenesis) which can be hard to keep track of. But the biggest thing is probably, like @NelliePledge says, that it's hard to truly know someone's caloric intake. There are many source of calories people don't even consider. I also feel like small differences in calories in/out can lead to a great convergence in weight over time.

 

[Utsikt]

Once it became obvious something had to change I got some scales and reduced my food intake until I began to lose weight. I was shocked not to mention disappointed at how little I could eat each day to continue losing weight.

Yeah, this was a big thing for me as well. It made me aim for an even lower intake so that I didn’t have to sit out in social situations. And I allowed myself my favourite pastry once a month.

 

[Utsikt]

I also feel like small differences in calories in/out can lead to a great convergence in weight over time.

1 egg a day = 3-4 kilos of fat worth of energy over a year. It’s nuts how much of a difference a little eating makes.

 

[Jonathan Edwards]

It’s received wisdom that the simple ratio of food intake to expenditure is the driving factor of weight, and one that deserves challenge.

It isn't the ratio, its the difference - subtraction.

And the evidence is solid as a rock - coming from people like my father who worked on healthy weight in air force pilots in the Second World War and later with the MRC and Hugh De Wardener who studied starvation and nutrient requirements in Japanese prisoners of war, of which he was one.

And let's face it, there isn't a plausible scientific alternative.

Overweight and obesity are due to eating more calories than are being used. The reasons why you eat more than you need are of course very complex, but nobody ever got fat from eating hardly anything - as De Wardener and others studying prisoners and concentration camp inmates discovered. Take an overweight person and give them an oesophagectomy and their weight plummets like a stone, however little they claimed to eat. Body calorimeters and Harpenden callipers do not lie. Metabolic rates between individuals may vary a bit but it makes no difference to the basic point. However much a person needs, they will only put on weight if they eat more.

 

[Hoopoe]

I also think that we live in a society with neoliberal values, that is motivated to reduce every failure to a character flaw of an individual, instead of looking at other factors that have a powerful influence on that individual's behaviour (but that would require admitting that we don't have as much free will as we thought we had...).

The obesity epidemic was a collective choice by society. Not a direct, conscious choice, but the consequence of its values, priorities and political decisions.

If healthy foods were affordable and easy to obtain while unhealthy obesity promoting foods were costly and not widely available then, I suspect, the obesity epidemic would end quickly. In a society that valued health, this is how it would be.

 

[Jonathan Edwards]

The obesity epidemic was a collective choice by society.

Largely a choice by the food and drink industry. Intensive research into addictive flavours and textures.

 

[Hoopoe]

Largely a choice by the food and drink industry. Intensive research into addictive flavours and textures.

They were allowed to do that because in a neoliberal society, government interference in the private sector must be minimized.

 

[NelliePledge]

Largely a choice by the food and drink industry. Intensive research into addictive flavours and textures.

Yes Dr Chris van Tulleken highlights how tobacco companies moved in on food production taking their production and marketing ethos with them.

 

[jnmaciuch]

It may well be true that it's difficult to compare calories between people, but there are plenty of skinny people who overeat like crazy, barely exercise and still don't end up obese. I'm one of them. By all accounts, I should be twice my size easily.

I also have the knowledge from several friendships in college and summer camps where I was literally spending every minute of every day with a group of people--where I ended up privy to all of their most shameful secrets and personal health issues and exactly what they were hiding in places they thought no one knew about (some of which was much more shame-inducing than snacking). I was the one washing the dishes and throwing out everyone's trash, so I got a very good sense of how much we were all eating relative to each other.

Is it possible that all of those friends were compulsively horking down thousands of calories in the few minutes where I didn't see them in the bathroom and were so effective at hiding the evidence that I never once caught wind of it? Maybe.

But overall I think the more likely scenario is just that "weight = (apparent) calories ingested - (apparent) calories expended" is an insufficient model for a large portion of the population. Which doesn't mean it's completely off the mark in every case--there are plenty of people who do reliably lose weight when they cut down on sweets. But there are plenty who don't--who make every single effort towards dieting and exercise and still can't lose more than the first 20 pounds. I think it's a fallacy to believe that the model must hold up in all cases because it seems to hold up in some, especially when there definitively is contradictory evidence.

Which shouldn't be a surprise to us here, considering that most people can also recover from overexertion overnight and can reliably increase their tolerance to physical activity by exercise training. All models are wrong, after all, it's just that some models are more useful than others. And in this case, I think there is clear social harm being done by blindly believing that this model must hold up in all cases (even though it seems to hold up in some).

You could choose to believe that all the thousands of people who have diligently tried every diet and exercise regimen in the book and failed to maintain a normal weight are simply lying or horrendously miscalculating. Or you could acknowledge that, just like some people seem genetically predisposed to be skinny despite eating a truckload of garbage every day, confounding biology beyond our current understanding could easily play a role in the other direction [edit: of which access to processed foods might be part of, but hardly the whole story]. I personally think that's a much more logical conclusion than believing that everybody could maintain a normal weight if they just ignored their cravings even though its hard sometimes.

 

[jnmaciuch]

And let's face it, there isn't a plausible scientific alternative.

common sense always seems to hold up until it doesn't

 

[Jonathan Edwards]

It may well be true that it's difficult to compare calories between people, but there are plenty of skinny people who overeat like crazy, barely exercise and still don't end up obese. I'm one of them. By all accounts, I should be twice my size easily.

But that doesn't affect the point I was making. You have no reason to think the calories somehow disappeared without being consumed. That happens in type 1 diabetes of course, and people lose weight rapidly, but there is no other way out for molecules.

Is it possible that all of those friends were compulsively horking down thousands of calories in the few minutes where I didn't see them in the bathroom and were so effective at hiding the evidence that I never once caught wind of it? Maybe.

Very possible, but maybe more likely they had been eating more before. Summer camps do not tend to last long enough to lose a visible amount of weight. And they may have been more efficient at appearing to be physically active while burning less claories but again that isn't the point. If they were overweight they had been eating more than they needed to.

But overall I think the more likely scenario is just that "weight = calories ingested - calories expended" is an insufficient model for a large portion of the population.

So what is the reasoning? The above are irrelevant. How did all those experiments in 1955 with total body calorimetry get things wrong?

 

[Jonathan Edwards]

there are plenty of people who do reliably lose weight when they cut down on sweets. But there are plenty who don't--who make every single effort towards dieting and exercise and still can't lose more than the first 20 pounds.

Presumably you have never lived with a secret eater. I have. It is all very subtle and invisible, except when things slip up.

 

[jnmaciuch]

Very possible, but maybe more likely they had been eating more before. Summer camps do not tend to last long enough to lose a visible amount of weight. And they may have been more efficient at appearing to be physically active while burning less claories but again that isn't the point. If they were overweight they had been eating more than they needed to.

And eating less would have involved starving themselves to the point of losing bodily function. Which did happen in a few friends who clearly developed anorexia as a consequence of narratives about weight and yet never got recognized as such because they couldn't possibly be restricting food intake if they were still fat.

 

[Jonathan Edwards]

common sense always seems to hold up until it doesn't

It isn't a matter of common sense. It was a matter of years of painstaking study. I remember my father showing me his equipment and how he used it.

 

[Utsikt]

Is it possible that all of those friends were compulsively horking down thousands of calories in the few minutes where I didn't see them in the bathroom and were so effective at hiding the evidence that I never once caught wind of it? Maybe.

You don’t need to be horking down. An egg a day adds 3-4 kilos a year. That’s well within the margins of guesstimates.

But there are plenty who don't--who make every single effort towards dieting and exercise and still can't lose more than the first 20 pounds.

I’m not sure if you meant it, but effort doesn’t matter. Compliance to the budget does.

I think it's a fallacy to believe that the model must hold up in all cases because it seems to hold up in some, especially when there definitively is contradictory evidence.

I personally think that's a much more logical conclusion than believing that everybody could maintain a normal weight if they just ignored their cravings even though its hard sometimes.

I’m an economist and I have a special interest in personal economy. The average person does not have a clue about their spendings - at best they guesstimate. So many people wonder why they don’t have more money at the end of the month, but if you gave me their banking info, I could show them where every cent went. They are usually shocked and in denial.

I have a very hard time believing that the average person is any better at keeping track or their caloric budget so to speak, even when trying. It’s a lot more complicated and abstract. That is not a character flaw, in my eyes. But it is a flaw with their execution.

If someone were able to track every single thing they put into their mouth and their weight over six months, I would believe it as a contradiction. And that would be using their kitchen scale for every ingredient. In the absence of that, I’m sceptical about there actually being contradictions.

 

[Jonathan Edwards]

And eating less would have involved starving themselves to the point of losing bodily function. Which did happen in a few friends who clearly developed anorexia as a consequence of narratives about weight and yet never got recognized as such because they couldn't possibly be restricting food intake if they were still fat.

Surely that is another non-sequitur. Eating a bit less would initially lead to normalising weight. Then they could eat a. little more. It's called dieting. Anorexia nervosa is a very real problem, as is bulimia but that just proves the point. Weight goes up and down with intake.

 

[Jonathan Edwards]

I was amused to remember just now a comment my father made at family dinner table around 1965. "Exercise doesn't actually make that much difference. It is how much you eat that largely determines your weight." Seems nothing has really changed.

 

[jnmaciuch]

Presumably you have never lived with a secret eater. I have. It is all very subtle and invisible, except when things slip up.

I also have! And it was very different than the situations I'm describing. Again, you can feel free to believe that dozens of people I knew throughout my life are secretly horking down way more than I do on a daily basis. Or you could acknowledge that the current paradigm is insufficient

It isn't a matter of common sense. It was a matter of years of painstaking study. I remember my father showing me his equipment and how he used it.

And like I said--it's a model that seems to hold up in some. Just like models of exercise training and increasing physical activity very clearly hold up in most of the population and then fail spectacularly for certain cases.

You don’t need to be horking down. An egg a day adds 3-4 kilos a year. That’s well within the margins of guesstimates.

I’m not sure if you meant it, but effort doesn’t matter. Compliance to the budget does.


I’m an economist and I have a special interest in personal economy. The average person does not have a clue about their spendings - at best they guesstimate. So many people wonder why they don’t have more money at the end of the month, but if you gave me their banking info, I could show them where every cent went. They are usually shocked and in denial.

I have a very hard time believing that the average person is any better at keeping track or their caloric budget so to speak, even when trying. It’s a lot more complicated and abstract. That is not a character flaw, in my eyes. But it is a flaw with their execution.

If someone were able to track every single thing they put into their mouth and their weight over six months, I would believe it as a contradiction. And that would be using their kitchen scale for every ingredient. In the absence of that, I’m sceptical about there actually being contradictions.

I do understand your concerns here, I really do. And believe me, I would have been sharing those thoughts several years ago. It's only through several deeply painful personal experiences that I realized everything I thought I knew about weight was wrong.

Like I said, I don't expect people to take me at my word, especially when I'm not going to take the time to trot out those personal narratives. I can just give personal attestation that I was also sitting there insisting that some of these friends must simply be calculating wrong, they must simply be unaware of something important, until the total amount of evidence accumulated that classical narratives of weight gain can't account for everything I'm seeing.

[Edit: and, I'll note, one of those experiences was watching a friend do exactly what you describe down to the kitchen scale for the purposes of losing weight for a life saving surgery. The surgery went fine even though they didn't lose weight--after trying for nearly a year with a level of diligence I found superhuman. They eventually found a surgeon who was competent enough to do their job on a fat patient]

I think this same "blindness" you describe here absolutely runs in the opposite direction in terms of evidence against this oversimplified model. There is such a deeply culturally ingrained belief that maintaining weight is a common sense paradigm, and people will jump through a million hoops to explain why someone who stuck with diets for years simply didn't do it right and that's why they are still fat. What I've learned through those experiences is that fatphobia is one of the most insidious cultural narratives I have ever witnessed. It's violent and it's deadly. But everyone is walking around acting like it doesn't exist. I'm very glad to have had people in my life that challenged me sufficiently, and it took an enormous amount of patience on their part until I realized I was wrong and deeply apologized

 

[jnmaciuch]

If anyone is interested, the Maintenance Phase podcast does a really great job of discussing the failures of weight loss paradigms and the social harm perpetuated through them.

Alright, now I really do have to bow out and get back to my work.

 

[Eleanor]

I remember reading something a few years ago about how lab rats are getting heavier despite being on the same calorie-controlled diets as in previous decades.